Metacity theme support is a compile time option. If you compile compiz with support for it then compiz-gtk does _require_ metacity to work.
travis@sorrow:~$ ldd /usr/bin/gtk-window-decorator | grep meta libmetacity-private.so.0 => /usr/lib/libmetacity-private.so.0 (0xb7e34000)
Metacity theme support is a compile time option. If you compile compiz with support for it then compiz-gtk does _require_ metacity to work.
travis@sorrow:~$ ldd /usr/bin/ gtk-window- decorator | grep meta
libmetacity- private. so.0 => /usr/lib/ libmetacity- private. so.0 (0xb7e34000)